The present disclosure relates to a light source apparatus and an image display apparatus using the light source apparatus.
Recently, products including solid-state light sources such as a light-emitting diode (LED) and a laser diode (LD) have been increasingly used. The solid-state light sources are adopted as light sources used in projectors for presentation and digital cinema, instead of mercury lamps, xenon lamps, and the like used in related art. The solid-state light sources such as LEDs have advantages such as having long lifetime, no replacement of lamps, which is necessary in related art, and lighting-up immediately after power-on.
Such a projector includes a type in which a solid-state light source such as an LED is directly used as a light source. On the other hand, there is another type in which a light emitter such as a phosphor, which is excited by excitation light to emit light, is used as a light source. In this case, the solid-state light source is used as an excitation light source that outputs excitation light.
For example, Japanese Patent Application Laid-open No. 2012-8303 proposes an optical system in which a collimated laser light beam is collected onto a phosphor by using a convex lens (see paragraph [0014], FIG. 1, etc. of Japanese Patent Application Laid-open No. 2012-8303). Further, Japanese Patent Application Laid-open No. 2012-37681 proposes an optical system including mirrors arranged in a stepwise manner and convex lenses. In this optical system, intervals of light fluxes from a plurality of light sources are narrowed by the mirrors arranged in the stepwise manner. Then, light is collected onto a phosphor by the convex lenses (see paragraph [0052], FIG. 1, etc. of Japanese Patent Application Laid-open No. 2012-37681).
Furthermore, Japanese Patent Application Laid-open No. 2012-58638 proposes an optical system in which a light collecting optical system is used instead of convex lenses in order to collect light from a plurality of light sources in a small space. This light collecting optical system is formed of an aggregate of small lenses, in which a plurality of small lenses each having a planar incidence plane and an aspherical-convex emission plane are arranged. An incidence plane of the light collecting optical system is a continuous plane, and an emission plane of the light collecting optical system is provided with a difference in level such that a center thereof recedes more along an optical axis of the light source apparatus (see paragraph [0038], FIG. 4, etc. of Japanese Patent Application Laid-open No. 2012-58638).